Places for autistic young people to hang out online

Hey, do you know of any good forums/resources for autism spectrum teens to hang out online? For example, a group that plays Minecraft together? My sister is one of the few autistic / socially disabled people at her school, and she tells me she feels really lonely a lot. I’d love to point her towards good resources, but there are so few for young people.
realsocialskills said:
I think, first of all, it depends on what her goals are. This is a kind of situation in which it could be really, really easy to fall into the trap of treating her as an acceptance object. I believe that connecting with other autistic young people is likely to be a really good idea and that it’s great that you want to make that possible for her. But I also think that ultimately what I think and what you think is much, much less important than what she thinks.
With that in mind, Tumblr might be a good option for her, if she’s interested.
There are a lot of autistic teenagers on Tumblr. If she specifically wants to talk about autism stuff, she might like the #actuallyautistic tag. (You shouldn’t post in that tag though, unless you are also autistic. If you want to ask autistic people questions, #askanautistic is a good resource, as is the Parenting Autistic Children With Love And Acceptance Facebook group.
Even if she is not particularly interested in discussing autism, Tumblr can be a good place to interact with other autistic teenagers. Most fandom tags contain autistic people talking about fandom, and many contain autistic people talking about autistic headcanons. For instance, a lot of autistic people talk about Animorphs, Bob’s Burgers, Harry Potter, Community, and Sherlock. 
One caveat: A lot of people on Tumblr are very pleasant to interact with, but there are also a lot of bullies who can be really aggressive. In order to enjoy Tumblr, it’s important to be selective about who you interact with. Blocking mean people makes Tumblr a lot more fun. (The presence of bullies doesn’t mean using Tumblr is a bad idea. The only way to prevent autistic people from encountering bullies is to prevent them from ever interacting with *anyone*, and that’s a lot worse than dealing with bullies.)
There’s also a browser extension called xkit that has a lot of extensions which make Tumblr more usable. Two in particular are helpful for avoiding bullies: blacklist and postblock. Blacklist allows you to block particular keywords, including URLs of mean people. Postblock allows you to block a particular post and never see it again, even if it is reblogged by people you follow. Those are really useful for avoiding mean people and cruel posts.
Twitter can also be a good place to hang out. It makes it easy to start conversations with a broad range of people, including some public figures. If there’s something she really enjoys talking about, Twitter might be a place to find people who are as into it as she is and aren’t tired of hearing about it. (That makes life a lot better. One of the hardest things about being an autistic teenager is lack of access to people who actually want to hear about your special interests. The internet makes that much better.)
Regarding Minecraft: There are also a couple of autism-specific Minecraft servers. I don’t know anything about them, so I can’t tell you if they are good or not. One of them is called Autcraft. That said, if she’s interested in playing Minecraft online, World of Minecraft is an all-ages server with nice people who make an effort to make it safe for kids too. It has both creative and survival modes and doesn’t allow PvP, griefing, or general obnoxiousness. She might enjoy that.
Do any of y'all have suggestions? Where are some good places for autistic young people to hang out online?